<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>

  </style>
</head>

<body>
  <div id="app">
    {{arr}} ==== {{total}}
    <input type="text" v-model="total">
  </div>
  <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.7.14/vue.min.js"></script>
  <script>
    const an = new Vue({
      el: '#app',
      data: {
        arr: [1, 2, 3, 4, 5],
        val: '',
        str: '123'
      },
      methods: {

      },
      computed: {
        total: {
          get() {
            return this.str
          },
          set(newVal) {
            this.str = newVal
          }
        }
      }
    })
  </script>
</body>

</html>